1. Field of the Invention
Embodiments of the present invention relate to an organic light emitting display device and a display panel thereof.
2. Description of Related Art
Recently, an organic light emitting display device has come into the spotlight. Organic light emitting display devices may have advantages such as a fast response rate, high light emitting efficiency, high luminance, and a wide viewing angle. These advantages may be attributable to the use of an organic light emitting diode, which emits light by itself.
In such an organic light emitting display device, pixels including organic light emitting diodes respectively are arranged and brightness of selected pixels by a scan signal is controlled depending on gradation of data.
Each pixel of such an organic light emitting display device may include a data line and a gate line which intersect each other, and transistors and a storage capacitor which are connected to the data line and the gate line, as well as the organic light emitting diode.
Each pixel of the organic light emitting display device may further include a driving transistor for driving the organic light emitting diode, where the driving transistor has a threshold voltage as an inherent characteristic value.
The threshold voltage of the driving transistor may vary as a driving time becomes longer. In this case, luminance of the corresponding pixel may not be achieved at a desired level, and/or a luminance difference between pixels may occur, thereby degrading the image quality. In some cases, the luminance difference causes a shortened durability of the corresponding driving transistor.
Accordingly, a compensation technology senses the threshold voltage of the driving transistor of each pixel and compensates for the threshold voltage of the driving transistor.
However, with this threshold voltage compensation technology, there is a problem in that compensation for the threshold voltage of the driving transistor can be established only within a predetermined range. That is, when the threshold voltage of the driving transistor increases above a specific value, or decreases below a specific value, there is a problem in that the threshold voltage compensation technology has a compensation limit in which the varied threshold voltage cannot be compensated for.
Therefore, there is a problem in that the pixel compensation technology may not be able to adequately compensate for the threshold voltage, thereby causing the quality of an image to degrade, and the driving transistor to be incapable of being driven for a long time.